Process of making metal halides



Patented Feb. 4, 1947 LINKED STATES PATENT FFICE 2,415,346 enemies OFMAKING lVIETALfHALiDE-S Henry V. Farr, Ferguson, .Mo., assignor to Mal--linckrodt Chemical Works, St. Louis, M6,,- a corporation-of Missouri NoDrawing. ApplicationNovember 13, "1943,-

' Serial No. 510,220

s claims. 1 This invention relates to processes for making metal salts,and with regard to certain more specific features, to processes formaking --metal halides.

This application is a'continuation-in-part of my copending applicationSerial No. 264,487, filed March 2'7, 1939.

Among the several objects of the invention may be noted the provision ofprocesses of the class described which commence with readily available,cheap raw materials, which raw materials are available in high degreesof purity, and from these raw materials prepare, in a simple andexpeditious manner, the desired metal halide 5 product, likewise in ahigh degree of purity; withlout necessitating long and involvedpurification steps; the provision of processes of the classde- -scribedwhich, in addition, produce as by-products certain halogen acids inrelatively high degrees of purity, which halogen acids are of them-;selves economically useful; and the provision of processes of the classdescribed which aresimple and economical to carry out. 'be in partobvious and in part pointed out here- :inafter.

Other objectswill (M being the metal in question, X being onehalogen,and Y being another-halogen; and n being the valence of M.) Theequilibrium of this reaction depends upon many factors most of whichneed not-be gone into herein. The most important factor herein concernedis, according tomy observations, that the reaction appears to pro-' ceedtowards the side of the equation inwhich the metal M is combined withthe1halogen of relatively greater atomic weight. For example, I havefound that if Y in the above reaction is chlorine and X is bromine, thereaction" proceeds toward the right-hand side of the equation;similarly, if Y is fluorine and X is chlorinathe-reaction also proceedstoward the right-handside'of the equation. 'By removal of thehydrohalide I-IY, -for example by boiling, the reaction proceeds- 55Obtainedypracticallyg. or entirely: freeqof hydrobromic orhydriodicacids, andwhatever hydro- 2 -.progressively;toward the right, and withsufiicient .boiling ;the reaction may be made to proceed tocompletioniinthe indicated direction.

The product acid, HY, .may be recovered in usefuliform .by any methodwhich selectively re- ..moves it-without significantfcontamination withthe reagent.acid 'II-Ihiscan conveniently be accomplished, :,forexample, by continuously re- .moving -..theproduct acid from :thereaction by fractional. distillation.

Thev situation as above 1 described is most -for- 'tunate from acommercial standpoint, because numerous .metal :chlorides are readilyavailable 1 at: low. cost in veryhig-h; degrees of purity as startingmaterials for the reaction,.and chlorine has thelowest atomic Weight(excepting fluorine) of ithet'halogens.

:Hydrobromic. and hydriodic acids, as starting -materials, are likewiseavailable in. high. degrees of-pur'ity.

For example, if a mixture of potassiumv chloride is made,: for instance,with hydrobromic or hydriodic acid, and the mixture isheated,hydrochloric acid may be removed by evaporation, leavingpotassium bromide or. potassium iodide. In

carrying-out this procedure, it appears most con- "ven-ient to mix thepotassium chloride with the hydrobromic or hydriodic acid-and then todistill off a mixture-of hydrogen-chloride gas and constant boilingaqueous hydrochloric acid. After most of the hydrogen chloride has comeover,

sufficient water is added-to dissolve all-of the salt, and thedistillation is resumed. By distilling oif this mixture through a shortfractionating column, the; hydrochloric acid distillate may bebromicorhydriodic.acidjs recoveredmay be returned to the. reactionvessel.

Aparticular feature of the reaction carriedout as... above :is: that,through .the use of pure. start- ..ing materialspwhich arereadilyavailable, the products. obtained,1namely, the metal halide, and

the hydrchalide, care 1 both. obtained; initially at high degreesofpurity, without .thenecessityof carrying through numerous purificationsteps such asrecrystallization; distillations and the like.

The hydrogen chloride obtained in..the example set forth. above; forexample, is free of practically all impurities and may be obtainedinpart at a least of any desired strength. '..*The= producthydrohalideisthus a valuable hy-product, ofthe reaction.

-.:If the reaction. is. carried: through using; the exact theoreticalproportion of the startinghydrohalide, it is frequently somewhatdifiicult to distill 01f the last of the product hydrohalide. Aconvenient method which has been evolved to solve this difficulty is toadd an excess of the starting hydrohalide and to carry out thedistillation through a fractionating column connected with an absorberfor collecting the product hydrohalide. When the greater part of theproduct hydrohalide has distilled off, water is added in amountsufficient to dissolve all of the remaining salt and the distillation iscontinued until practically all of the product hydrohalide has distilledover and the major part of the residual metallic halide has crystallizedout. After cooling, then, the liquor which contains the excess ofstarting hydrohalide together with any residual product hydrohalide, isremoved by suction from the crystals, and the crystals are rinsed withwa ter to remove all of the mother liquor. The mother liquor may then beused without disadvantage in preparing the next reaction batch, sincethe product hydrohalide which it contains will readily distill over whenthe next batch is heated, according to the reaction given.

An advantage of the process of th present invention is that itapparently proceeds with all metals that form in aqueous solution thedescribed type of halogen salts, namely, those corresponding to theformula MXn, regardless of the hydrohalide used, provided the atomicweight criterion set forth above is followed. Typical of the metalswhich do not satisfy the foregoing requirement as to the formation ofthe desired type of halogen salts, is the metal gold. Gold salts inaqueous solution form haloauric acids when treated with acids. Similarlythe tetravalent halides of palladium, iridium and platinum do notsatisfy the foregoing requirement. These halides likewise formhalometallic acids in aqueous solution when treated with acids. Themetals which do form in aqueous solution the described type of halogensalts, that is, those corresponding to the formula MXn, are well knownto those skilled in the art.

The process of the present invention apparently proceeds even withmetals whose halogen salts tend to hydrolyze to form oxyhalides if asulficient concentration of the acid H)! is maintained in the reactionmixture to prevent hydrolysis.

Without limiting the generality of the foregoing, the following areseveral specific examples illustrating the process of the presentinvention:

Example 1 149 grams of technical potassium chloride and 507 grams ofconstant boiling hydrobromie acid (48% HBr) were placed in adistillation apparatus and boiled. The salt-did not dissolve completely.During the first ten minutes of the distillation, substantially onlygaseous hydrogen chloride was evolved. This was absorbed'in ice water.After about ten minutes, liquid began to come over. After 161 grams ofdistillate (total gas plus liquid) had been collected, the distillationwas stopped and 200 cc. of water was added. This is suflicient todissolve all of the salt. The distillation was then resumed and 229grams of distillate were collected. At this point, a considerablequantity of salt had crystallized out in the distillation flask.

The distillate was analyzed, and found to contain (considering allportions) substantially 100% of the theoretical amountof hydrogenchloride, together with a very small amount of hydrogen bromide.

The salt and mother liquor in the distillation flask were treated asfollows: The mother liquor was filtered oif and the salt was washedtwice by stirring with ice water and filtering with suction. The saltwas then spread on a watch glass and dried in an electric oven at 110 C.for eighteen hours. The dried salt weighed 150 grams.

The combined wash liquors were then placed in the distillation apparatusand boiled down until the salt started to crystallize out. Then themother liquor was added, and the boiling continued until very littleliquor remained. The residue was then filtered and washed as before withtwo portions of ice water, and the recovered salts dried over night at110 C. The salt thus recovered weighed 55 grams, making a total recoveryof 205 grams, which is about 86% of the theoretical yield. On analysis,the salt was shown to be practically KBr.

Example 2 149 grams of technical potassium chloride and 800 gramshydriodic acid (48% HI) were placed in a distillation apparatus andboiled. The salt dissolved completely. During the early stages of thedistillation no gaseous hydrogen chloride came over, but only liquid. Atotal of 312 grams of distillate was collected, which, on analysis, wasshown to contain practically the entire theoretical amount of hydrogenchloride, together with a very small amount of iodine and hydrogeniodide.

At this point a considerable quantity of salt had crystallized out inthe distillation flask. The contents of the distillation flask were thentransferred to an open vessel and evaporated to complete dryness. Thisyielded 310 grams of potassium iodide (96% of the theoretical yield)practically entirely free of potassium chloride.

Example 3 A portion of sodium fluoride and an excess of aqueoushydrochloric acid were mixed together in a platinum evaporating dish andheated to dryness. The remaining product, upon analysi was shown to bepractically pure sodium chloride.

Example 4 A portion of potassium bromide and an excess of aqueoushydriodic acid were mixed and evaporated to dryness in an open vessel.The remaining product, upon analysis, was shown to be potassium iodidewith only a small amount of potassium bromide.

Example 5 Hydrobromic acid (660 grams) of 49% concentration and cuprouschloride (198 grams) were placed in a distilling flask connected to acondenser and the mixture brought to boiling at C. Boiling was continueduntil the temperature reached C. 447 grams of distillate were collectedin ice water durin this interval and the residue in the flask was acrystalline slurry amounting to 414 grams. The solid was filtered,washed with N/lO hydrobromic acid and dried. Cuprous bromide (191 grams)was obtained. Upon analysis it was found to be practically pure cuprousbromide.

Example 6 Following the procedure described in Example 5, zinc chloride(136 grams) and hydrobromic acid (362 grams) of 49% concentration wereboiled together until considerable salt had separated in the flask andthe mixture became quite thick. 237 grams of 'distillate'were collected.

The reaction mixture was then placed in an evaporating dish andevaporated to dryness forming 215 grams of solid. Upon analysis this wasfound to be practically pure zinc bromide.

Example 7 Following the procedure described in Example 5, dihydratedbarium bromide (167 grams) and hydriodic acid (532 grams) of 48%concentration were boiled together until considerable salt had separatedin the distilling flask and the mixture became fairly thick. 460 gramsof distillate were obtained. The solid was removed from the reac-v tionmixture by suction and dried at 100 C. forming 14.0 grams of product.The filtrate was evaporated on a steam bath and dried forming 36 gramsof dried salt. The products were substantially pure barium iodide.

Example 8 acid (125 cc.) of 48% concentration. After the evolution ofcarbon dioxide had ceased, the solution was evaporated to drynessforming the theoretical amount of calcium fluoride. Calcium fluoride (39grams) formed as described and hydriodic acid (255 grams) of 48%concentration were placed in a platinum evaporating dish and heated forseveral hours, adding hydriodic acid from time to time to replace thatlost by evaporation until a total of 865 grams had been used. Anadditional 225 grams of hydriodic acid were then added and the hotliquor filtered. The filtrate was boiled down to cc. and upon cooling asolid cake weighing 63 grams was obtained. Upon analysis this productwas found to be almost pure calcium iodide, with water and a very smallamount of calcium hydroxide. The calcium hydroxide was apparently formedby decomposition from heat of a small portion of the calcium iodide.

Example 9 Following the procedure described in Example 5, manganouschloride tetrahydrate (396 grams) was placed in a distilling flask andhydrobromic acid (347 grams, which is about half of'theoretical requiredfor complete conversion) of 49% concentration was added. The mixture wasboiled until it had become fairly thick at which point 363 grams ofdistillate had been collected and the boiling point had risen to 117 C.Upon standing overnight the residue in the flask solidifled andsufficient distilled water was added to dissolve the salt when hot, theresulting solution poured into evaporating dishes and'heated overnight.The resulting solution was allowed to cool and crystals formed. Thesewere filtered off and the filtrate again evaporated until crystals beganto separate. After this mixture was allowed to cool it was filtered andthe salt and filtrate placed in separate evaporating dishes and heatedat 70 C. to apparent dryness. The total weight of salt thus obtained was541 grams. A sample was analyzed and was found to contain 25.0%manganese, 31.1% bromine, 15.1% chlorine and 28.6% water. From theseanalyses it is seen that the product was a mixture of substantiallyequimolecular quantities" of manganous chloride and manganous bromideExample 10 Sodium fluoride (21 grams) and concentrated hydrochloric acid(96 grams) were placed in a dish and evaporated to dryness with frequentstirring. 30.5 grams of dry salt were obtained. The product uponanalysis Was shown to contain 98.24% of sodium chloride.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

" As many changes could be made in the above processes without departingfrom the scope of the invention, it is intended that all mattercontained in the above description shall be interpreted as illustrativeand not in a limiting sense.

I claim:

1. In the process of making halogen salts of metals that form in aqueoussolution halogen salts of the type MXn, by reacting a salt of the typeMY with an acid of the type HX, where M is the desired metal, X is thedesired halogen, n is the valence of M and Y is another halogen of loweratomic weight than X, the improvement comprising treating said salt witha substantially equivalent quantity of said acid in aqueous solutionwith suficient water to form a constant boiling mixture and separatingthe product acid from the halogen salt produced.

2. In the process of making halogen salts of metals that form in aqueoussolution halogen salts of the type MXn, by reacting a salt of the typeMY with an acid of the type HX, where M is the desired metal, X is thedesired halogen, n is the valence of M and Y is another halogen of loweratomic weight than X, the improvement comprising heating said salt witha substantially equivalent quantity of said acid in aqueous solutionwith sulficient water to form a constant boiling mixture and separatingthe product acid from the halogen salt produced.

3. In the process of making alkali metal halides of metals that form inaqueous solution halogen salts of the type MX, where M is the metal andX is halogen, by reaction of aqueous solutions of the hydride of thedesired halogen with a salt of the type MYn, where M is the desiredalkali metal, Y is another halogen of lower atomic weight than thedesired halogen, and n is the valence of M, the improvement comprisingtreat-- ing said salt with a substantially equivalent quantity of saidacid in aqueous solution with sufficient water to form a constantboiling mixture and separating the product acid from the halogen saltproduced.

4. In the process of making metal iodides of the type ML; of a metalthat forms in aqueous solution salts of the type MIn, by the reaction inan aqueous medium of hydrogen iodide on a metal salt MY, where M is thedesired metal, Y is a halogen of lower atomic weight than iodine, and nis the valence of M, the improvement comprising treating said salt witha substantially equivalent quantity of said acid in aqueous solutionwith sufficient water to form a constant boiling mixture and separatingthe product acid from the halogen salt produced.

5. In the process of making metal bromides of the type of MBrn of ametal that forms in aqueous solution salts of the type MBI'n, by thereaction in an aqueous medium of hydro-gen bromide on a metal salt MY,where M is the desired metal,

Y- is a halogen of lower atomic weight than bromine, and n is thevalence of-M,- the improve ,ment comprising treating said salt with asubstantially equivalent quantity of said acid in aqueous solution withsufiicient water to form a constant boiling mixture and separating theproduct acid from the halogen salt produced.

6. In the process of making potassium'iodide by reaction in aqueousmedium of hydrogen iodide with the potassium salt of a halogen of loweratomic weight than iodine, the improvement comprising treating said saltwith a substantially equivalent quantity of said acid in aqueoussolution with suflicient water to form a constant boiling mixture. andseparating the product acid from the halogen salt produced.

7. In the process of making cup-rous bromide by reaction in aqueousmedium of hydrogen bromide with cuprous chloride, the improvementcomprising treating said cuprous chloride with a substaintiallyequivalent quantity of said hydrogen bromide in aqueous solution withsufiicient water to form a constant boiling mixture and separating theproduct acid from the cuprous bromide produced.

8 8. In the process of making calcium iodide by' reaction in aqueousmedium of hydrogen iodide with calcium fluoride, the improvementcomprising treatingsaid calcium fluoride with a substantially equivalentquantity of said hydrogen iodide in aqueous solution with suificientwater to form a constant boiling mixture and separating'the product acidfrom the calcium iodide produced.

HENRY V. FARR.

REFERENCES CITED The following references are of record in the file ofthis patent:

Fremys "Encyclopedia Chimique, Tome III, Metaux, 2nd Cahier, part 1,Potassium, pages 49 and 50 (1887). I q

Mellors Comprehensive Treatise on Inorganic and Theoretical Chemistry,vol. III, page 606 (1922).

Mellors Comprehensive Treatise on Inorganic and Theoretical Chemistry,1927, vol. VII, page 81.

